Vitamin D is different from other essential vitamins because our bodies can store it as well as manufacture it. When our skin is exposed to sunlight then the body can synthesize and make it. If your body cannot produce enough vitamin D because of insufficient sunlight exposure then it needs to be obtained from supplements and dietary sources.
There aren't many foods that contain vitamin D. The best sources are considered to be:
- fish such as salmon, tuna, mackerel, sardines and herring
- fish liver oils
- beef liver
- egg yolks
There are five forms of vitamin D - vitamin D1, D2, D3, D4, D5. The two most important forms for the human body are vitamins D2 (ergocalciferol) and D3 (cholecalciferol).
Healthy body weight
Vitamin D probably plays an important role in maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.
The study attempted to determine whether baseline vitamin D levels before calorie restriction affect subsequent weight loss. Circulating blood levels of vitamin D were measured in 38 overweight men and women before and after the subjects followed a calorie restricted diet plan for 11 weeks. Subjects also had their fat distribution measured. The study found that pre-diet vitamin D levels predicted weight loss - for every increase of 1 ng/mL precursor form of vitamin D subjects ended up losing almost a half pound more on their diet and for each 1-ng/mL increase in the active form of vitamin D subjects lost nearly one-quarter pound more. Additionally, higher pre-diet vitamin D levels (both the precursor and active forms) predicted greater loss of abdominal fat. The authors concluded that "the results suggest the possibility that the addition of vitamin D to a reduced-calorie diet will lead to better weight loss" but cautioned that more research is needed.
Vitamin D is crucial for the absorption and metabolism of calcium and phosphorous, which is especially important for the maintenance of healthy bones. Perhaps the best known Vitamin D deficiency disease is childhood rickets, which is characterized by soft, weak bones.
For post-menopausal women who are at higher risk of osteoporosis, taking vitamin D along with calcium supplements can reduce the rate of bone loss, help prevent osteoporosis, and may reduce the risk of fractures.
Keeps your heart healthy
The benefits of Vitamin D include helping the heart in general. Population studies suggest that people with low levels of vitamin D have a greater risk of developing heart disease, including heart attack, stroke, and heart failure compared to people with higher levels of vitamin D. Low levels of vitamin D may increase the risk of calcium build-up in the arteries. Calcium build-up is part of the plaque that forms in arteries when you have atherosclerosis and can lead to a heart attack or stroke. Other population studies show that people with lower levels of vitamin D are more likely to have risk factors for heart disease, including high blood pressure, type 2 diabetes, obesity, and high cholesterol.
Boosts your Immune System
Vitamin D is said to be an immune system regulator. It may be an important way to arm the immune system against disorders like the common cold.
A study published by the Executive Director of the Vitamin D Council showed these benefits of Vitamin D:
- Children who go out in the sun are less likely to catch colds.
- Flu season peaks in the months that have the shortest periods of daylight.
- Flu virtually disappears in midsummer.
- Taking a cod liver oil supplement, one of the best sources of Vitamin D, reduces viral respiratory infections, such as colds and flu.
- Even in the tropics, with so much sunlight, flu is more common during the rainy season.
- UVB sunlamps, which produce Vitamin D in the skin, reduce colds and flu in schoolchildren.
- Doctors who gave high doses of Vitamin D to children constantly sick from colds and flu found that the kids became free of infection.
Maintains cognitive functions
Studies have shown that low levels of vitamin D are linked to a decline in cognitive performance.
Two papers published in an issue of Neurology show in separate populations that low levels of vitamin D are associated with cognitive impairment and cerebrovascular disease, including stroke. The first concluded that inadequate vitamin D is associated with cognitive impairment in elderly women and that vitamin D supplements may improve or maintain cognitive function. The second concluded that vitamin D deficiency is associated with an increased risk for dementia and cerebrovascular disease and that vitamin D may have vasculoprotective properties.